java - Hibernate cannot simultaneously fetch multiple bags -

hibernate throws exception during sessionfactory creation:

org.hibernate.loader.multiplebagfetchexception: cannot simultaneously fetch multiple bags

this test case:

parent.java

@entity public parent {   @id  @generatedvalue(strategy=generationtype.identity)  private long id;   @onetomany(mappedby="parent", fetch=fetchtype.eager)  // @indexcolumn(name="index_col") if had problem solve retrieve more children have, 1 child null.  private list<child> children;  } 

child.java

@entity public child {   @id  @generatedvalue(strategy=generationtype.identity)  private long id;   @manytoone  private parent parent;  } 

how problem? can do?

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edit

ok, problem have "parent" entity inside parent, real behavior this:

parent.java

@entity public parent {   @id  @generatedvalue(strategy=generationtype.identity)  private long id;   @manytoone  private antoherparent anotherparent;   @onetomany(mappedby="parent", fetch=fetchtype.eager)  private list<child> children;  } 

anotherparent.java

@entity public antoherparent {   @id  @generatedvalue(strategy=generationtype.identity)  private long id;   @onetomany(mappedby="parent", fetch=fetchtype.eager)  private list<anotherchild> anotherchildren;  } 

hibernate doesn't 2 collections fetchtype.eager, seems bug, i'm not doing unusual things...

removing fetchtype.eager parent or anotherparent solves problem, need it, real solution use @lazycollection(lazycollectionoption.false) instead of fetchtype (thanks bozho solution).

i think newer version of hibernate (supporting jpa 2.0) should handle this. otherwise can work around annotating collection fields with:

@lazycollection(lazycollectionoption.false) 

remember remove fetchtype attribute @*tomany annotation.

but note in cases set<child> more appropriate list<child>, unless need list - go set